Lab Safety, Measurements, and Beer-Lambert Law
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How do you dilute a strong acid?
Add the acid to the water, the water will help disperse the heat from this exothermic reaction. If you added water the acid then the acid with spatter everywhere.
heat up test tubes using?
• a water bath, not an open flame - use a test tube holder
Before you ever weigh something on a weigh paper, you ALWAYS need todo what?
always need to tare the paper on the scale
how do you properly transfer a powdered reagent to weigh paper?
pure reagent onto a paper and transfer the reagent to pre-tared paper from that, never remove reagent with a devise OR put reagent back into bottle to avoid contamination
Always measure liquid reagents in a graduated cylinder from the?
Meniscus, the curved bottom
How to use pH meter?
Calibrate probe with pH4 or pH10, rinse probe with dionized water between samples/measurements, dab the probe dry after rinsing with deionized water
transparent
allows light to pass through
opaque
no light can pass through
absorption
refers to the amount of light a substance allows to pass through it
a completely transparent substance does not ____ light?
Does not absorb any light (zero absorbance or 100% transmission)
a completely opaque substance ______ light?
absorbs all light (100% absorbance or 0% transmission)
spectrophotometry
analysis of a substance to determine its amount of light absorbance. How much light a substance absorbs is a unique quality of that substance and can help ID it from another substance
Beer-Lambert’s Law
Absorbance =Ecl • E (epsilon)= molar extinction coefficient • c = sample’s concentration • l = path length (distance between the light source and the detector in the spectrophotometer)
substance that are brightly colored have higher or lower molar extinction coefficients?
Higher
A substance’s light absorbance can be numerically conveyed by using an equation called?
Beer-Lamberts Law absorbance =Ecl
Are absorbance and concentration directly proportionally in Beer-Lamberts Law?
Yes